The present invention involves methods of preparing coated particulates and using such coated particulates in subterranean applications such as production enhancement and sand control. More particularly, the present invention relates to methods of preparing particulates treated with an adhesive substance (such as a tackifying agent or curable resin) such that the particulates are able to resist sticking and clumping and need not be immediately used once they are prepared.
Subterranean operations often use particulates coated with an adhesive substance such as a tackifying agent or a curable resin. One example of a production stimulation operation using such coated particulates is hydraulic fracturing, wherein a formation is treated to increase its permeability by hydraulically fracturing the formation to create or enhance one or more cracks or “fractures.” In most cases, a hydraulic fracturing treatment involves pumping a proppant-free, viscous fluid (known as a pad fluid) into a subterranean formation faster than the fluid can escape into the formation so that the pressure in the formation rises and the formation breaks, creating an artificial fracture or enlarging a natural fracture. Then particulates known in the art as proppant are placed into the fracture to prevent the fracture form closing when the pumping pressure is released. A portion of the proppant may be coated with an adhesive substance to control the migration of the proppant particulates and/or to control the migration of formation sands and fines.
An example of a well completion operation using a treating fluid containing coated particulates is gravel packing. Gravel packing treatments are used, inter alia, to reduce the migration of unconsolidated formation particulates into the well bore. In gravel packing operations, particulates known in the art as gravel are carried to a well bore by a hydrocarbon or water treatment fluid. That is, the particulates are suspended in a treatment fluid, which may be viscosified, and the treatment fluid is pumped into a well bore in which the gravel pack is to be placed. The treatment fluid leaks off into the subterranean zone and/or is returned to the surface while the particulates are left in the zone. The resultant gravel pack acts as a filter to separate formation sands from produced fluids while permitting the produced fluids to flow into the well bore. A portion of the gravel may be coated with resin or tackifying agent, inter alia, to further help control the migration of formation fines. Typically, gravel pack operations involve placing a gravel pack screen in the well bore and packing the surrounding annulus between the sand control screen and the formation (or casing) with gravel designed to prevent the passage of formation sands through the pack. The sand control screen is generally a type of filter assembly used to support and retain the gravel placed during the gravel pack operation. A wide range of sizes and screen configurations are available to suit the characteristics of a particular well bore, the production fluid, and the subterranean formation sands. Such gravel packs may be used to stabilize a portion of a formation while causing minimal impairment to well productivity. The gravel is generally designed to prevent formation sands from occluding the screen or migrating with the produced fluids, and the screen is generally designed prevent the gravel from entering the well bore.
In some situations the processes of hydraulic fracturing and gravel packing are combined into a single treatment to provide stimulated production and an annular gravel pack to reduce formation sand production. Such treatments are often referred to as “frac pack” operations. In some cases, the treatments are completed with a gravel pack screen assembly in place, and the hydraulic fracturing treatment being pumped through the annular space between the casing and screen. In such a situation, the hydraulic fracturing treatment usually ends in a screen out condition creating an annular gravel pack between the screen and casing. This allows both the hydraulic fracturing treatment and gravel pack to be placed in a single operation.